It is estimated that 1.4 to 2 million people in the USA suffer from Systemic lupus erythematosis (SLE). At present, there is no cure for SLE. The pathogenesis of SLE is still unknown. Studies have suggested that cytokines may play an important role in its pathogenesis. Tumor necrosis factor alpha (TNFalpha) is a cytokine with very diverse physiological and pathological activities. Several lines of evidence have suggested that TNFalpha play an essential role in the development and progression of SLE. First, it has been reported that TNFalpha production in activated monocytes from SLE patients is significantly decreased. Second, it has also been shown that lupus patients with low TNFalpha production have an increased incidence of lupus nephritis. Lastly, in a SLE murine model, the levels of TNFalpha production by activated macrophages are significantly lower in NZW lupus prone mice. Treatment with recombinant TNFalpha significantly reduces the incidence of lupus nephritis in these mice. Recent studies have demonstrated that reduced production of TNFalpha in NZW lupus-prone mice is mainly regulated at the translational level, mediated by the 3' untranslated region (3'UTR) of the TNFalpha gene. In this project, I will dissect the 3'UTR of the TNFalpha gene and characterize its role in the regulation of TNFalpha production. My specific aims are: 1. To delineate the translational regulatory cis-acting elements in the TNFalpha 3'UTR of NZW lupus-prone mice through deletion and site- directed mutagenesis using transient transfection assays with the luciferase reporter system. 2. To test whether the RNA-protein binding profile is different between the mutated 3'UTR of the lupus-prone NZW mouse and the non-mutated 3'UTR of the non-lupus-prone mouse and to further characterize the trans- acting factors involved in regulating the T'NFalpha gene. The elucidation of the mechanism of regulation of TNFalpha production is fundamental in understanding the pathogenesis of SLE, with possible implications in SLE treatment through manipulation of TNFalpha production. Accomplishment of the proposed project also has the potential to enhance our understanding of post-transcriptional gene regulation in general.